How long does a "weight loss plateau" last? I'm using South Beach and lost 10 pounds in two

[Broken_Hero]

6. At the time between 1200-1600 calories a day.

I after two weeks I upped my bike riding from 18 miles to 24 plus. After another two weeks I decided to add a mile and a half walk to my 24 mi bike ride. I heard that if you do the same exercise all the time your body gets use to it, and you might have to shock it a bit by doing a different type of exercise, so I added walking. After two weeks of doing 24 miles on bike, and 1.7 my plateau was still in effect, and my heart was basically destroyed and frustration was my constant partner. After 6 week of trying to break it by adding more exercise, I went back to my initial 18+miles for a couple more weeks before I threw in the towel. I couldn't break 347, as a matter of fact I'd gain to 350, and bounce back down to 347 but I couldn't break it.